An efficient message-routing system, an essential component of a multi
computer, allows communication between any two processes of a concurre
nt program wherever they are located on a parallel computer network. I
t simplifies the concurrent software development on multicomputers by
separating the hardware architecture from the software configuration o
f processes. This article surveys some implemented routers for transpu
ter networks and compares them for adaptivity, deadlock freedom, netwo
rk latency, generality, and livelock freedom.